Improved Competitive Guarantees for QoS Buffering

Abstract

C e n t r u m v o o r W i s k u n d e e n I n f o r m a t i c aImproved Competitive Guarantees for QoS Buffering ABSTRACT We consider a network providing Differentiated Services (Diffserv), which allow Internet Service Providers (ISP's) to offer different levels of Quality of Service (QoS) to different traffic streams. We study two types of buffering policies that are used in network switches supporting QoS. In the FIFO type, packets must be transmitted in the order they arrive. In the uniform boundeddelay type, there is a maximum delay time associated with the switch and each packet must be transmitted within this time, or otherwise it is dropped. In both models, the buffer space is limited, and packets are lost when the buffer overflows. Each packet has an intrinsic value, and the goal is to maximize the total value of transmitted packets. Our main contribution is an algorithm for the FIFO model with arbitrary packet values that for the first time achieves a competitive ratio better than 2, namely 2 -epsilon for a constant epsilon > 0. We also describe an algorithm for the uniform bounded delay model which simulates our algorithm for the FIFO model, and show that it achieves the same competitive ratio. AbstractWe consider a network providing Differentiated Services (Diffserv), which allow Internet Service Providers (ISP's) to offer different levels of Quality of Service (QoS) to different traffic streams. We study two types of buffering policies that are used in network switches supporting QoS. In the FIFO type, packets must be transmitted in the order they arrive. In the uniform bounded-delay type, there is a maximum delay time associated with the switch and each packet must be transmitted within this time, or otherwise it is dropped. In both models, the buffer space is limited, and packets are lost when the buffer overflows. Each packet has an intrinsic value, and the goal is to maximize the total value of transmitted packets. Our main contribution is an algorithm for the FIFO model with arbitrary packet values that for the first time achieves a competitive ratio better than 2, namely 2 − for a constant > 0. We also describe an algorithm for the uniform bounded delay model which simulates our algorithm for the FIFO model, and show that it achieves the same competitive ratio.

Lower and Upper Bounds on FIFO Buffer Management in QoS Switches

“…Note that their modification does not improve the overall performance of the strategy [6]. The best known lower bound on the competitive ratio of this problem is ≈ 1.419 [9].…”

“…Kesselman, Mansour, and van Stee [9] introduce the preemptive greedy strategy and prove that this strategy achieves a competitive ratio of ≈ 1.983. In addition, they give the previously best known lower bound of (1 + √ 5)/2 ≈ 1.618 on the competitive ratio of the preemptive greedy strategy.…”

“…We study the preemptive greedy strategy (PG) introduced in [9]. This is a simple strategy that can be implemented efficiently.…”

“…Kesselman, Mansour, and van Stee [9] introduce the preemptive greedy strategy (PG) with the parameter β > 1. When a packet p arrives, PG does the following.…”

Comparison-Based FIFO Buffer Management in QoS Switches

“…Kesselman, Mansour, and van Stee [12] give the state-of-the-art algorithm pg, and prove that pg is 1.983-competitive. Additionally, they give a lower bound of (1 + √ 5)/2 ≈ 1.618 on the competitive ratio of pg and a lower bound of 1.419 on the competitive ratio of any deterministic algorithm.…”